The present invention relates to a magnetic recording/reproducing apparatus which forms on a magnetic tape an information recording area apart from recording areas for a video signal and an audio signal.
In general, as a method for removing unnecessary signal portions (for example, a commercial portion) from signals to be recorded by a magnetic recording/reproducing apparatus (hereinafter referred to as the VTR), such unnecessary signal portions are inhibited from being recorded. With this method, however, the user must operate the VTR each time an unnecessary signal portion appears during a recording operation. This method may also cause the user to make mistakes, e.g., forgetting to record necessary portions.
To avoid such mistakes, conventionally, all signals, including unnecessary portions, are in many cases recorded, and an operation such as a search is performed upon reproducing the signals by a VTR each time an unnecessary portion is to be skipped. This method takes much time and labor.
As one of the methods to solve the above-mentioned problems, as described in JP-A-59-221851, a technique for a VTR has been proposed in which an information signal is recorded together with a video signal such that an operation mode such as a search is automatically controlled by the recorded information signal. Specifically, the operation mode of the VTR is controlled in accordance with particular bit pattern information of an ID signal in a PCM audio signal. This technique is based on the idea that time information, a field number, stereo/monaural discrimination information and so on, conventionally written on a magnetic tape, are not always necessary. Although this prior art allows the user to control the operation of the VTR without giving the user trouble, since an information signal is recorded together with a PCM audio signal in a PCM audio region, the PCM audio signal must be processed together every time the user is to execute so-called after-recording, i.e., an operation for recording an information signal after a video signal has been recorded, erasure, re-recording and so on. Also, the information signal, since recorded in the PCM audio area, cannot be commonly used with time information and other information such as a field number.
To cope with the above-mentioned problem, a technique, as described in JA-A-64-79990, has been proposed where an information signal recording area is formed in part of a slant track with respect to the longitudinal direction of the tape where neither a video signal nor an audio signal is recorded, and data for editing, as well as a time code and so on, are recorded in this information signal recording area. Since the data for editing is recorded in an area separate from areas for recording video and audio signals, this prior art permits the user to after-record such data for editing.
However, as the second prior art technique requires a program created for specifying an operation mode of a VTR at a particular tape position to be recorded at the beginning of a tape, the creation and recording of the program takes much time and labor. Also, if reproduction is started from a midway point of a tape, the VTR cannot read data for editing, whereby the specified operation is not performed by the VTR. Further, since the data for editing must be temporarily stored in an editor, the editor needs a memory and its control circuit, and accordingly becomes very expensive.
Although the foregoing first prior art does not give rise to an inconvenience even if reproduction is started from a midway point of a magnetic tape since a particular bit pattern is recorded at a position where the operation of a VTR is to be switched, the particular bit pattern alone cannot be after-recorded as described above. In addition, this prior art does not indicate specific procedures for recording and reproducing the particular bit pattern and thus fails to consider the operability of the VTR.
It will be understood by those skilled in the art that reading of the information signal for search and fast-forward operations is the first to be considered. Specifically explaining, when a magnetic tape is transported at a high speed during such operations, magnetic heads obliquely scan a plurality of tracks at intervals, as is well known in the art. For this reason, the magnetic heads may not scan a track including an area in which an information signal is written, whereby the operation of the VTR is possibly hindered. To cope with this problem, it has been proposed to record the same information on a plurality of tracks. However, the above-mentioned prior art does not indicate specific means for doing this. Such recording of the same information on a plurality of tracks, however, is not preferable from a viewpoint of effective utilization of a recording area on a magnetic tape. Generally, in a search or fast-forward operation which need not read the information signal, the number of tracks on which the same information is recorded should be as small as possible. The prior art does not consider in which mode information is read, and accordingly gives rise to a problem with respect to effective utilization of a recording area.
In addition, when another information signal indicating an operation mode or the like is to be after-recorded on a magnetic tape on which an information signal including sequential information such as a time code has been written upon recording a video signal, the previously recorded sequential information such as the time code is erased by the after-recording operation.
Since the operation of the VTR is controlled after an information signal is read from a running magnetic tape, a time lag from the reading of the information signal to the start of the control and the influence of inertia caused by the tape-cylinder system give rise to a problem that a requested operation is started from a position of a tape slightly advanced from the desired position. This problem is grave, particularly when a still reproduction is specified, because a slight deviation of track may result in reproducing a completely different video signal.
When an information signal alone is to be re-recorded, for example, because of a positional error of recording, if the recorded position of the information signal is not known, erroneous operation may occur due to a failure of erasure or an incomplete erasure of the information signal.